Question

How many numbers between 400 and 700 are divisible by 9 or 11?

Answer 1

Hi ,

i ) 405 ,414 , ...., 693 are numbers between

400 to 700 divisible by 9

This is clearly in A.P.

first term ( a ) = 405

common difference ( d ) = a2 - a1

d = 414 - 405 = 9

let number of terms = n

an = 693

a + ( n - 1 )d = 693

405 + ( n - 1 )9 = 693

divide each term with 9 , we get

45 + n - 1 = 77

n = 77 - 44

n = 33